Method of tapering tubes



Dec. 4, 1934. J. K. JAMISON 1,982,874

METHOD OF TAPERING TUBES 2 Sheets-Sheet 1 Filed Aug. 12, 1933 INVENTOR,

wnussses M 2531M A g, 5 m. QMJJM Mam/M Dec. 4, 1934. J. K. JAMISON METHOD OF TAPERING TUBES Filed Aug. 12, 1.933 2 Sheets-Sheet 2 wnuzssss Mam/-0 Patented Dec. 4, 1934 1,982,874 METHOD OF TAPERING TUBES John Kenneth Jamison,

to Hamilton Standar Monessen, Pa., assignor d Propeller Company,

Hartford, Own, a corporation of Delaware Application August 12, 1933, Serial No.

13 Claims. (01. 29-156) This invention relates to the manufacture of aeronautical propellers, and it has to do especially I with thetapering and accurate sizing of tubular blanks for use in making the blades of such propellers.

Among the objects of the invention are to proworking one end of by reduction of diameter.

In the production of aeronautical propellers it 15 is important to obtain uniform mass distribution in the blades in order to avoid the setting up ofunbalanced stresses in use. Particularly is this the same and distribution as every other and type.

Generally speaking the means and methods herein claimed as my invention comprise the use of a preliminary series of tapered ring dies, each 5 smaller than and or" slightly reduced taper compared to the preceding one, and having interiors that in the aggregate substantially define the ex terior taper which it is intended to impose on the indrical tubular blank. The largest of these dies is used first, the tube being forced through it until the die reaches the point on the blank where the taper is to commence. Then the next smaller die is forced over the reduced cylindrical portion beyond the tapered step left by the final positioning of the largest die. The second die is moved to final position to form a second tapered step substantially continuouswith that produced by the first die. This process is repeated with each of the dies, in order of size. The final result is a tapered swaged or die-sunk end of predetermined slope and size on the tube, with slight differences in the taper of the successive steps.

Then a mandrel having exactly the size and taper desired for the interior of the tubular blank is placed in the tube, and the tube seated on the forced into a final series of of the tapered portion. The final result is that the tapered portion of the blank is reduced to the exact internal taper and size determined by the mandrel.

Having reference form terminal fiange 2. This may be done by any suitable operation, and preferably but not necessarily the flange is formed before tapering the tube.

end of the-preceding tapered the last tapered step at the tip of the tube.

wise reduction is .the reduced portion generally tip 6 of the mandrel does not Thus there is provided a blank 10. (Figs. 5 and 6) having a continuous series of tapered adj oining steps 4,411, 4b, etc., of progressively decreasing diameter, each step being of a slightly reduced taper compared to the next larger step. In actual practice thediscontinuity between successive tapered steps is not sharply defined, although the reduction is apparent. The stepped character of the tapered portion may, however, be observed by placing a straight edge along its side. For purposes of illustration and description the stepshown on an exaggerated scale in Fig. 5. 1

There is next inserted in blank 1a a mandrel 5 having a tapered tip 6, the dimensions of which correspond to the final internal dimensions desired in the tapered part of the blank. As seen in Figs. 5 and 6, sinking dies 3, 3a, etc., conform but not exactly to the desired final taper. This permits the man;- drel to be inserted with a neat fit. The tapered make continuous contact with the interior of the reduced portio of the blank'because of the step-like characteg of the latter, but on the contrary makes contact only at spaced intervals, such as near the inner end of each step. This leaves intermediate spaces or pockets 7 (Fig. 5) betweenthe mandrel and the inner wall of the blank.

The blank is now the mandrel by driving it into tapered swaging dies 8, 8a, and 8b successively. These dies are tapered and their outlet and irilet openings are correlated in' the manner described for the preliminary sinking dies 3, 3a, etc.

This final swaging operation is positioning the tapered end of the blank dies 8, 8a, 8b, in turn, and then driving the mandrel with success've heavy blows until the tube has been stretched and swaged and driven onto the mandrel to shape of the mandrel in the die. Pockets '7 provide a space for free flow of the adjacent metal when deformed in the swaging dies. Thus the metal does not back up and res t plastic deformation, and the swaging die and mandrel cooperate to produce a smooth external and interperformed by in the nal taper 9, Fig. 8, conforming to the mandrel tip and die, and therefore accurately sized internally.

After the final swaging operation has been completed, the mandrel slides freely from within It is desirable to drel and the outer surface of the blank during the swaging operations, and the manner in which the metal has conformeditself may be observed from the lubricant distribution over the mandrel tip when it is slipped out at the end of the swaging step. The uniformity of metal flow shows in the lines made in the lubricant by flow and by the internal surface of the blank.

This method produces blanks in which internal machining operations are substantially eliminated, because the taper is accurately sized internally, and because the metal is deformed smoothly and uniformly. The processes described produce accurately sized and tapered tubes',.but the wall thickness of seamless tubing varies materially in diiferent tubes. Consequently, the final wall thickness is not always the same even though the internal dimensions may be exactly the same. Therefore after the tube has been tapered and sized as above described it is reduced to final exact dimensions throughout by forced over and down on bring the interior down to the step-taper is machining the ex erior to an exact relation to the sized interior. This gives a wall thickness of predetermined dimensions at all points. This final machining to a fixed relation to a sized interior is not a part of the present invention, having been previously known and practiced. It is not therefore illustrated or described in detail.

The tip of the blank may be closed in any suitable manner, as by spinning, to remove excessplicable to other metals. It is preferred to conduct both the preliminary sinking and the final swaging operations cold. The die-sinking operations work the metal severely, and it is in general necessary to anneal, or in the case of steel, to normalize,

in each die, in order to avoid injury to the metal at a subsequent stage of the process.

As a specific example of the practice of the invention, there may be mentioned the production of propeller blade blanks from chromemolybdenum steel tubes about four with an outside diameter of 5.1 inches and a wall thickness of 0.25 inch. These tubes are subjected {to cold-sinking in a series of six dies, such as those shown in Figs. 4 to 4e. Die 3 has an inlet opening of 5.1 inches, corresponding to the outside diameter of the blank, and its outlet opening is 4.5 inches, this being also the inlet size of die 3a. The outlet of die 3a, is 4 inches in diameter, that of die BD 3.5 inches in diameter, of, die 30 8 inches in diameter, of die 3d 2.5 inches in diameter, and of die 3e 2 inches.

After reduction in each of the sinking dies the steel blank is normalized by heating it to about 1650 F; cooling below the critical point, i. e. to about 1200 F., in the furnace, and then aircooling it, when it is ready for the next reducing "ioperation. No intermediate annealing or normalizing treatment is necessary after the first of the final swaging operations, because there each section of metal is workedbut once.

The tapered reduction is conducted over a distance of approximately '17 inches. from the end of the tube. There is now inserted in the step-reduced blank a mandrel having a tapered tip 195 inches in length dimensioned to produce the desired internal taper in the blank. This contacts with the tube in substantially the manner shown in Fig. 5. The blank is then swaged in a series of three tapered dies, such as those shown in Fig. '7. Swaging' die 8b has an inlet openinggof 5.1 inches and an outlet opening" of 4.0 inches, which corresponds to the inlet of die 8a. The outlet of die 8a and the inlet of die 8 is 2% inches, while the outlet of the latter is 1% inches. In the swaging operation the 17-inch elongated to approximately 19.5 inches. The metal varies uniformly in wall thickness from an exterior diameter of 5.1 inches at its larger end to an exterior diameter of 1% inches at its tip. The wall thickness of the tube increases slightly during the sinking and swaging operations, but this change in thickness does not prevent the interior taper being smooth, uniform, and accurately dimensioned, and such'excess is removed in final exterior machining.

the blank following reduction feet in length,

practicing my invention According to the provisions of the patent statutes, I have explained the principle and mode of and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. A method of forming a tapered blank from a tube, comprising reducing one end of the blank radially and progressively in tapered steps of decreasing-diameter, inserting in the blank a tapered mandrel having an exterior of dimensions desired for the interior of the blank, swa ing the blank on the mandrel in ring dies and thereby converting its stepped reduced portion to a smooth taper interiorly conforming in shape and dimensions to the mandrel taper.

2. A method of making tapered hollow metallic propeller blade blanks, comprising the steps, of progressively reducing one end of a metallic tube radially in steps of successively decreasing diameter to form a stepped tapered portion, and then swaging said portion over a mandrel having a tapered tip inserted in said stepped portion and thereby conforming the interior of the stepped portion to said mandrel.

3. A method of making tapered hollow metallic propeller blade blanks, comprising the steps of progressively and radially reducing one end of a metallic tube to form a series of tapered steps of successively decreasing diameter conforming generally 'to the desired taper, and then swaging the stepped portion over a mandrel having a tapered tip inserted in said portion and thereby smoothing the stepped portion to the mandrel taper.

4. A method of making tapered hollow metallic propeller blade blanks comprising reducing one end of the blank radially and progressively in steps of decreasing diameter to form a stepped portion conforming generally to the desired taper, inserting in the blank a mandrel having a tapered tip which contacts at spaced intervals with said portion to form intervening pockets, and dieswaging the blank on the mandrel, and thereby smoothing said stepped portion to a uniform taper accurately sized interiorly.

5. A method of making tapered hollow metallic propeller blade blanks, comprising the steps of sinking one end of a hollow cylindrical blank progressively in a series of dies of successively decreasing size to form a stepped portion conforming generally to the desired taper, inserting in the blank a mandrel having a tapered tip dimensioned to produce the desired taper and contacting with the tervals, and swaging the stepped portion over said mandrel to plastically convert it to a smooth taper of substantially accurate internal size.

6. A method of making tapered hollow metallic propeller blade blanks, comprising the steps of die sinking one end of a hollow cylindrical blank progressively to form a series of tapered steps conforming generally to the desired taper, inserting in the blank a mandrel having a. taper productive of that desired, and die-swaging the stepped portion over said mandrel to plastically conform said stepped portion to the mandrel and form a smooth taper of substantially accurate internal size.

7. A method of making tapered hollow metallic ropeller blade blanks, comprising the steps of stepped portion at spaced indie sinking one end of a hollow tube progressively and radially to form a series .of tapered steps conforming generally to the desired taper, in-

blank a mandrel having a tapered accurately to the taper of the mandrel.

8. A method of making tapered hollow metallic tapered mandrel the dimensions of which correspond substantially to the internal taper desired,

desired taper.

9. A method of making tapered hollow metallic propeller blade blanks, comprising the steps of sinking one end of a hollow cylindrical blank smoothly to an accurately sized taper.

10. A method of making tapered hollow metalerally to the desired taper, the die being substantially equal to the blank, and the inlet of eachsucceeding die 11. A method of making tapered hollow metal- 11c propeller blade blan of the blank through the tapered step pro tially continuous wit duced by the first die, 5 smaller dies until produced, then mandrel of external dim interior of the of tapered ring inserting in a second tapered die until duced thereby is substanh the tapered steps proand so on with successive the desired external taper is the blank a tapered ension desired for the blank, then forcing a second set dies over the tapered portion of JOHN KENNETH JAMISON. 

